Modern mower-conditioners are powered so that they may be towed at a relatively fast speed over the field. Due to the increased ground speed, the crop windrow is left flat with the crop stems oriented parallel with the direction of travel. The flat windrow seals the crop on the bottom from any air to dry the crop.
The problem to be solved is that of forming a windrow that will dry down in a relatively short time without requiring the ground speed of the mower-conditioner to be slowed below the cutting and windrow forming capacity of the mower-conditioner.